Thermal processing of miscanthus, sugarcane bagasse, sugarcane trash and their acid hydrolysis ...

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THERMAL PROCESSING OF MISCANTHUS, SUGARCANE
BAGASSE, SUGARCANE TRASH AND THEIR ACID
HYDROLYSIS RESIDUES
ANA MARÍA CORTÉS BENÍTEZ
Doctor of Philosophy
Chemical Engineering
ASTON UNIVERSITY
September 2014
© Ana María Cortés Benítez, September 2014
Ana María Cortés asserts her moral rightto be identified as the author of this thesis
This copy of the thesis has been supplied on condition that anyone who consults itis
understood to recognise that its copyright rests with its author and that no quotation
from the thesis and no information derived from it may be published without proper
acknowledgement.
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Aston University
Thermal processing of miscanthus, sugarcane bagasse, sugarcane trash and their
acid hydrolysis residues
Ana María CortésBenítez
Doctor of Philosophy
2014
THESIS SUMMARY
The research presented in this thesis was developed as part of DIBANET, an EC funded
project aiming to develop an energetically self-sustainable process for the production of
diesel miscible biofuels (i.e. ethyl levulinate) via acid hydrolysis of selected biomass
feedstocks. Three thermal conversion technologies, pyrolysis, gasification and
combustion, were evaluated in the present work with the aim of recovering the energy
stored in the acid hydrolysis solid residue (AHR). Mainly consisting of lignin and humins,
the AHR can contain up to 80% of the energy in the original feedstock. Pyrolysis of AHR
proved unsatisfactory, so attention focussed on gasification and combustion with the aim
of producing heat and/or power to supply the energy demanded by the ethyl levulinate
production process.
A thermal processing rig consisting on a Laminar Entrained Flow Reactor (LEFR)
equipped with solid and liquid collection and online gas analysis systems was designed
and built to explore pyrolysis, gasification and air-blown combustion of AHR. Maximum
liquid yield for pyrolysis of AHR was 30wt% with volatile conversion of 80%. Gas yield for
AHR gasification was 78wt%, with 8wt% tar yields and conversion of volatiles close to
100%. 90wt% of the AHR was transformed into gas by combustion, with volatile
conversions above 90%. 5volO %-95vol%N gasification resulted in a nitrogen diluted, low
2 2
heating value gas (2MJ/m3). Steam and oxygen-blown gasification of AHR were
additionally investigated in a batch gasifier at KTH in Sweden. Steam promoted the
formation of hydrogen (25vol%) and methane (14vol%) improving the gas heating value to
10MJ/m3, below thetypical for steam gasification due to equipment limitations.
Arrhenius kinetic parameters were calculated using data collected with the LEFR to
provide reaction rate information for process design and optimisation. Activation energy
(E ) and pre-exponential factor (k in s-1) for pyrolysis (E =80kJ/mol, lnk =14), gasification
A o A o
(E =69kJ/mol, lnk =13) and combustion (E =42kJ/mol, lnk =8) were calculated after
A o A o
linearly fitting the data using the random pore model. Kinetic parameters for pyrolysis and
combustion were also determined by dynamic thermogravimetric analysis (TGA),
including studies of the original biomass feedstocks for comparison. Results obtained by
differential and integral isoconversional methods for activation energy determination were
compared. Activation energy calculated by the Vyazovkin method was 103-204kJ/mol for
pyrolysis of untreated feedstocks and 185-387kJ/mol for AHRs. Combustion activation
energy was 138-163kJ/mol for biomass and 119-158 for AHRs. The non-linear least
squares method was used to determine reaction model and pre-exponential factor.
Pyrolysis and combustion of biomass were best modelled by a combination of third order
reaction and 3 dimensional diffusion models, while AHR decomposed following the third
order reaction for pyrolysis and the 3 dimensional diffusion for combustion.
Keywords: acid hydrolysis residue, thermal decomposition kinetics, thermogravimetric
analysis (TGA), laminar entrained flow reactor (LEFR).
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ACKNOWLEDGEMENTS
I would like to thank my supervisor Professor Tony Bridgwater for his guidance, advice,
patienceand support.
I would also like to thank Daniel and Surila for their invaluable support in the lab; and for
creating such an enjoyable working environment together with Emma, Irene, Kerri, Scott,
Clara, Nassir, Alejandro, Javier and Manisha.
I would like to express special thanks to Francis for his help with the cyclone design and
the reactor simulations; and to Steve Williams at the Glassblowing Facility in the
University of Birmingham for always finding time to repair my experimental setup.
I gratefully acknowledge the European Commission for financial support of the research
carried out under the FP7 DIBANET project “The Production of Sustainable Diesel-
Miscible-Biofuels from the Residues and Wastes of Europe and Latin America” (Grant
number 227248-2);and under the Biofuels Research Infrastructure for Sharing Knowledge
(BRISK) carried out at Royal Institute of technology KTH in Sweden.
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TABLE OF CONTENTS
THESIS SUMMARY..........................................................................................................2
ACKNOWLEDGEMENTS..................................................................................................3
TABLE OF CONTENTS....................................................................................................4
LIST OF FIGURES..........................................................................................................10
LIST OF TABLES............................................................................................................16
ABBREVIATIONS...........................................................................................................20
1. INTRODUCTION..................................................................................................21
1.1. DIBANET OBJECTIVES AND STRUCTURE.................................................22
1.1.1. Scientific objectives................................................................................22
1.1.2. Work packages (WPs)............................................................................22
1.1.3. Evolution of Work Package 4 (WP4).......................................................23
1.2. PRESENT WORK RESEARCH OBJECTIVES..............................................23
1.3. STRUCTURE OF THE THESIS.....................................................................25
2. FEEDSTOCK CHARACTERISATION...................................................................27
2.1. FEEDSTOCKS..............................................................................................27
2.1.1. Miscanthus giganteus.............................................................................27
2.1.2. Sugarcane trash.....................................................................................29
2.1.3. Sugarcane bagasse................................................................................30
2.1.4. Acid hydrolysis residue (AHR)................................................................30
2.2. DETERMINATION OF FEEDSTOCK COMPOSITION..................................32
2.2.1. Structural components separation..........................................................32
2.2.2. Particle size distribution of AHR..............................................................34
2.2.3. Elemental analysis and heating value.....................................................34
2.2.4. Proximate analysis.................................................................................36
2.2.5. Ash content dependence on particle size................................................37
2.3. THERMAL DECOMPOSITION ANALYSIS....................................................38
2.3.1. Untreated feedstocks..............................................................................38
2.3.2. Structural fractions..................................................................................40
2.3.3. TGA pyrolysis and combustion of AHR...................................................42
2.4. PYROLYSIS PRODUCTS ANALYSIS...........................................................44
2.5. INTERIM CONCLUSIONS.............................................................................47
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3. BIOMASS FAST PYROLYSIS AND VAPOUR CATALYTIC UPGRADING...........49
3.1. PRINCIPLES OF FAST PYROLYSIS............................................................49
3.2. PYROLYSIS MECHANISM............................................................................51
3.3. PROPERTIES OF BIO-OIL............................................................................52
3.4. CATALYTIC UPGRADING OF FAST PYROLYSIS VAPOURS.....................55
3.5. CATALYST SCREENING BY Py-GCMS.......................................................57
3.5.1. Reference works using integrated configuration (Figure 16a).................58
3.5.2. Reference works using mixed configuration (Figure 16b).......................58
3.5.3. Close-coupled configuration (Figure 16c)...............................................59
3.6. CATALYSTS FOR CATALYTIC PYROLYSIS AND VAPOUR UPGRADING.60
3.6.1. Zeolites...................................................................................................60
3.6.2. MCM–41 mesoporous materials.............................................................68
3.6.3. Other mesoporous catalysts...................................................................69
3.6.4. Metal oxides...........................................................................................71
3.6.5. Activated alumina...................................................................................73
3.6.6. Other catalysts.......................................................................................73
3.7. MATERIALS AND METHODS.......................................................................75
3.7.1. Feedstocks.............................................................................................75
3.7.2. Description of catalysts received from research partners........................75
3.7.3. Preparation of nickel phosphide catalyst.................................................76
3.7.4. Equipment..............................................................................................78
3.8. EXPERIMENTAL PLAN.................................................................................79
3.9. INTERIM CONCLUSIONS.............................................................................80
4. PRINCIPLES OF BIOMASS GASIFICATION.......................................................83
4.1. BACKGROUND.............................................................................................83
4.1.1. Gasification products..............................................................................84
4.1.2. Gasifier classification according to heating method................................85
4.2. TYPES OF GASIFIERS.................................................................................87
4.2.1. Fixed bed gasifiers.................................................................................88
4.2.2. Fluidised bed gasifiers............................................................................90
4.2.3. Entrained flow gasifiers...........................................................................91
4.3. GASEOUS AND LIQUID FUELS PRODUCTION FROM BIOMASS
GASIFICATION........................................................................................................91
4.4. HEAT AND POWER GENERATION FROM BIOMASS GASIFICATION.......92
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4.5. CURRENT STATUS OF GASIFICATION TECHNOLOGY.............................92
4.6. INTERIM CONCLUSIONS.............................................................................93
5. GASIFICATION OF MISCANTHUS AND ITS AHR AT KTH.................................95
5.1. LITERATURE REVIEW ON GASIFICATION OF HIGH LIGNIN CONTENT
RESIDUES...............................................................................................................95
5.2. MATERIALS AND METHODS.......................................................................98
5.2.1. Feedstocks.............................................................................................98
5.2.2. Gasification agents.................................................................................98
5.2.3. Gasification equipment at KTH...............................................................98
5.3. EXPERIMENTAL PLAN...............................................................................100
5.4. RESULTS AND DISCUSSION....................................................................101
5.4.1. Equipment issues.................................................................................101
5.4.2. Data generation....................................................................................103
5.4.3. Gasification results...............................................................................106
5.5. INTERIM CONCLUSIONS...........................................................................110
6. PRINCIPLES OF BIOMASS COMBUSTION......................................................112
6.1. COMBUSTION PROCESS..........................................................................112
6.1.1. Combustion equipment.........................................................................113
6.1.2. Biomass co-firing..................................................................................114
6.2. HEAT AND POWER GENERATION FROM COMBUSTION.......................114
6.3. INTERIM CONCLUSIONS...........................................................................115
7. THERMOGRAVIMETRIC DETERMINATION OF KINETIC PARAMETERS FOR
PYROLYSIS AND COMBUSTION OF BIOMASS AND AHRs...................................116
7.1. BACKGROUND TO DETERMINATION OF KINETIC PARAMETERS.........116
7.1.1. Kinetic equation and parameters..........................................................117
7.1.2. Experimental determination of decomposition curves...........................118
7.1.3. Kinetic parameter calculation for non-isothermal measurements..........118
7.1.4. Model-fitting methods...........................................................................120
7.1.5. Model-free approximations...................................................................123
7.1.6. Methods for determining pre-exponential factor and reaction model.....125
7.2. LITERATURE REVIEW OF APPLICATION OF METHODS.........................126
7.2.1. Pyrolysis studies...................................................................................126
7.2.2. Combustion studies..............................................................................131
7.3. MATERIALS AND METHODS.....................................................................134
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7.3.1. Preparation of samples.........................................................................134
7.3.2. Thermogravimetric analysis..................................................................134
7.3.3. Kinetic parameters estimation...............................................................135
7.4. RESULTS FROM TGA PYROLYSIS...........................................................136
7.4.1. TGA pyrolysis curves............................................................................136
7.4.2. Results from model-free isoconversional calculation.............................139
7.4.3. Results from ASTM method calculation................................................155
7.5. RESULTS FROM TGA COMBUSTION.......................................................156
7.5.1. TGA combustion curves.......................................................................156
7.5.2. Results from model-free non-isothermal calculation.............................160
7.5.3. Results from ASTM method calculation................................................173
7.6. INTERIM CONCLUSIONS...........................................................................174
8. DEVELOPMENT AND CONSTRUCTION OF A THERMAL PROCESSING MICRO-
REACTOR.................................................................................................................178
8.1. LITERATURE REVIEW ON DTR and LEFR................................................178
8.1.1. Reports on applications using Drop Tube Reactors (DTRs)..................179
8.1.2. Applications using Laminar Entrained Flow Reactors (LEFRs).............182
8.2. SUMMARY AND CONCLUSIONS FROM THE REVIEW.............................183
8.3. MICRO-REACTOR SPECIFICATIONS........................................................186
8.4. MICRO-REACTOR VERSION 1..................................................................187
8.4.1. Gas measurement and feeding.............................................................189
8.4.2. Powder fluidising feeding system..........................................................189
8.4.3. Collection of solids and liquids..............................................................191
8.4.4. Product gas cleaning and analysis........................................................192
8.4.5. Micro-reactor Version 1 characterisation...............................................192
8.4.6. Shortcomings of micro-reactor Version 1..............................................194
8.4.7. Proposed improvements for Version 1..................................................195
8.5. MICRO-REACTOR VERSION 2..................................................................196
8.5.1. Lambda doser feeding rate calibration..................................................198
8.5.2. Operation methodology for micro-reactor Version 2..............................199
8.5.3. Shortcomings of micro-reactor Version 2..............................................203
8.5.4. Proposed improvements for Version 1..................................................204
8.6. MICRO-REACTOR VERSION 3..................................................................204
8.6.1. Quartz micro-reactor (Version 3) characterisation.................................206
8.7. INTERIM CONCLUSIONS...........................................................................208
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9. AHR THERMAL DECOMPOSITION EXPERIMENTS IN THE LAMINAR
ENTRAINED FLOW REACTOR (LEFR)....................................................................210
9.1. REVIEW OF KINETIC MODELS USED IN LITERATURE...........................210
9.1.1. Volume reaction model.........................................................................212
9.1.2. Shrinking core model............................................................................213
9.1.3. Random pore model.............................................................................213
9.2. MATERIALS AND METHODS.....................................................................214
9.2.1. Laminar Entrained flow reactor.............................................................214
9.2.2. Feedstocks...........................................................................................214
9.2.3. Mass balance and conversion calculations...........................................215
9.2.4. Kinetic parameters calculation..............................................................215
9.3. LAMINAR ENTRAINED FLOW REACTOR RESULTS................................215
9.3.1. Feeding issues.....................................................................................217
9.3.2. Pyrolysis results....................................................................................218
9.3.3. Gasification results...............................................................................227
9.3.4. Combustion results...............................................................................234
9.4. INTERIM CONCLUSIONS...........................................................................240
9.4.1. LEFR performance...............................................................................240
9.4.2. Thermal processing..............................................................................241
10. CONCLUSIONS..............................................................................................243
10.1. EVALUATION OF COMPOSITION AND PROPERTIES OF BIOMASS
FEEDSTOCKS AND ACID HYDROLYSIS RESIDUES..........................................243
10.2. SELECTION OF CATALYSTS FOR ONLINE CATALYTIC UPGRADING OF
FAST PYROLYSIS VAPOURS..............................................................................245
10.3. DETERMINATION OF THE COMPOSITION OF PRODUCTS FROM
GASIFICATION OF MISCANTHUS AND ITS ACID HYDROLYSIS RESIDUE.......246
10.4. DETERMINATION OF ARRHENIUS KINETIC PARAMETERS OF
PYROLYSIS AND COMBUSTION PROCESSES USING TGA..............................247
10.5. DETERMINATION OF ARRHENIUS KINETIC PARAMETERS OF
PYROLYSIS, GASIFICATION AND COMBUSTION PROCESSES USING A
LAMINAR ENTRAINED FLOW REACTOR............................................................249
11. RECOMMENDATIONS...................................................................................252
11.1. TGA KINETIC ANALYSIS........................................................................252
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11.2. LAMINAR ENTRAINED FLOW REACTOR DESIGN AND PERFORMANCE
252
11.3. GASIFICATION OF AHR.........................................................................253
11.4. COMBUSTION OF AHR..........................................................................254
12. REFERENCES................................................................................................255
APPENDIX. LEFR TEMPERATURE PROFILES USING COMPUTATIONAL FLUID
DYNAMICS...................................................................................................................268
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